Take missed opportunity: memset for A8.

Just recently noticed we weren't doing this.
It seems to be triggering all the time.

Draws the same of course.

Change-Id: Ie3d869a05194a5d52d635643eba1c96c8a21ce67
Reviewed-on: https://skia-review.googlesource.com/8471
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/src/core/SkRasterPipelineBlitter.cpp b/src/core/SkRasterPipelineBlitter.cpp
index 197233c..87a76aa 100644
--- a/src/core/SkRasterPipelineBlitter.cpp
+++ b/src/core/SkRasterPipelineBlitter.cpp
@@ -224,16 +224,10 @@
 
     if (fCanMemsetInBlitH) {
         switch (fDst.shiftPerPixel()) {
-            // TODO: case 0: memset (for A8)
-            case 1:
-                sk_memset16((uint16_t*)fDstPtr + x, fMemsetColor, w);
-                return;
-            case 2:
-                sk_memset32((uint32_t*)fDstPtr + x, fMemsetColor, w);
-                return;
-            case 3:
-                sk_memset64((uint64_t*)fDstPtr + x, fMemsetColor, w);
-                return;
+            case 0:    memset  ((uint8_t *)fDstPtr + x, fMemsetColor, w); return;
+            case 1: sk_memset16((uint16_t*)fDstPtr + x, fMemsetColor, w); return;
+            case 2: sk_memset32((uint32_t*)fDstPtr + x, fMemsetColor, w); return;
+            case 3: sk_memset64((uint64_t*)fDstPtr + x, fMemsetColor, w); return;
             default: break;
         }
     }